Field of the Invention
The present invention relates to an exposure apparatus, an exposure method, and a device manufacturing method.
Description of the Related Art
Along with micropatterning of devices, extremely strict optical performance has been requested for the projection optical system of an exposure apparatus, and various imaging characteristic adjusting mechanisms such as a magnification adjusting mechanism and a distortion adjusting mechanism have been added. These imaging characteristic adjusting mechanisms mainly aim at correcting the assembly error of the projection optical system and correcting a change in imaging performance of the projection optical system caused by exposure heat. Japanese Patent Laid-Open No. 7-183214 has proposed an exposure apparatus including a correction system which corrects the projection magnification of a projection optical system. In the exposure apparatus described in Japanese Patent Laid-Open No. 7-183214, the projection magnification is adjusted in accordance with the shot magnification of a preceding shot, and is adjusted again in accordance with the shot magnification of a succeeding shot if the projection magnification for the preceding shot exceeds the tolerance of an alignment error of the succeeding shot.
Recently, a back-side illumination (BSI) sensor has been developed in order to improve the sensitivity of an image sensor. The BSI sensor is manufactured by bonding a device substrate to a supporting substrate to polish the back side of the device substrate, and then performing an overlay exposure of patterns such as a color filter and a microlens on the back side of the device substrate. A distortion is known to occur in this device substrate when bonding the device substrate to the supporting substrate to polish the back side of the device substrate. It is therefore necessary to perform an exposure by controlling the imaging performance (the magnification, the distortion, or the like) of the projection optical system in accordance with the distorted shape of the device substrate when performing the overlay exposure of the color filter, the microlens, and the like on the device substrate.
However, the imaging performance needs to be corrected greatly every time each shot is exposed because the distortion amount of this device substrate is large and the distortion shapes of the respective shots on the device substrate vary greatly. In the exposure apparatus in Japanese Patent Laid-Open No. 7-183214, the imaging performance of the projection optical system is corrected in accordance with the shot magnification of each shot, leading to a decrease in throughput because of its high frequency of correction.